Enabling mobile switched antennas

ABSTRACT

The claimed subject matter relates to enabling antenna switching in a wireless terminal that has multiple receive antennas per receive chain via soft-demodulation and interleaving of concatenated code received in a strip channel. A coherent demodulation protocol may be performed to estimate an SNR for a first antenna during a first time period, and a non-coherent demodulation protocol may be utilized on the strip channel to estimate an SNR for at least one other antenna during a second time period. SNRs may be compared and the terminal may select the antenna with the highest SNR for a next transmission superslot.

CROSS-REFERENCE

This application contains subject matter related to U.S. patentapplication Ser. No. 11/249,770, entitled METHODS AND APPARATUS FORTRANSMITTING SIGNALS FACILITATING ANTENNA CONTROL, filed on Oct. 13,2005, the entirety of which is hereby incorporated by reference.

BACKGROUND

I. Field

The following description relates generally to communications systems,and more particularly performing antenna switching to improve frequencydiversity in a wireless communication environment.

II. Background

Wireless networking systems have become a prevalent means to communicatewith others worldwide. Wireless communication devices, such as cellulartelephones, personal digital assistants, and the like have becomesmaller and more powerful in order to meet consumer needs and to improveportability and convenience. Consumers have become dependent upon thesedevices, demanding reliable service, expanded areas of coverage,additional services (e.g., web browsing capabilities), and continuedreduction in size and cost of such devices.

A typical wireless communication network (e.g., employing frequency,time, and code division techniques) includes one or more base stationsthat provides coverage areas to subscribers as well as mobile (e.g.,wireless) devices that can transmit and receive data within the coverageareas. A typical base station can simultaneously transmit multiple datastreams to multiple devices for broadcast, multicast, and/or unicastservices, wherein a data stream is a stream of data that can be ofindependent reception interest to a user device. A user device withinthe coverage area of that base station can be interested in receivingone, more than one or all the data streams carried by the compositestream. Likewise, a user device can transmit data to the base station oranother user device.

In conventional multiple-input multiple-output (MIMO) receivers, aseparate receive chain is required for each receive antenna. A stripchannel is a dedicated resource that may be utilized by a base stationfor broadcasting. For example a non-beacon strip channel may permit abase station to broadcast information in a prescribed format, wheninformation bits may be coded across one or more strip channels.However, conventional strip channels lack robustness when confrontedwith channel frequency selectivity, unreliable channel estimation, orthe like. An unmet need exists in the art for systems and/ormethodologies that mitigate interference and improve frequency diversityto overcome the afore-mentioned deficiencies.

SUMMARY

The following presents a simplified summary in order to provide a basicunderstanding of some aspects of the claimed subject matter. Thissummary is not an extensive overview, and is not intended to identifykey/critical elements or to delineate the scope of the claimed subjectmatter. Its sole purpose is to present some concepts in a simplifiedform as a prelude to the more detailed description that is presentedlater.

According to various aspects, a method of decoding a communicationsignal may comprise receiving a set of symbols containing a plurality ofinformation bits, dividing the received set of symbols into a pluralityof subsets of symbols, each subset corresponding to the input of aninner code demodulation selecting a set of initial a priori values ofthe inner code demodulation for each subset of symbols, and demodulatingeach subset of symbols, using the initial a priori values of the subsetof symbols and an inner code generator matrix, to generate a pluralityof first soft information values as the output of the inner codedemodulation. The method may further comprise associating each of thefirst soft information values to one of the plurality of informationbits using an outer code generator matrix, calculating a plurality ofsecond soft information values as the output of the outer codedemodulation, wherein each second soft information value corresponds toone of the information bits and is calculated using at least two of thefirst soft information values associated with the information bit,determining a new set of a priori values of the inner code demodulationfor each subset of symbols, using the second soft information values andthe outer code generator matrix, and replacing the initial a priorivalues with the new a priori values, and repeating the demodulating,associating, calculating and determining actions at least once.

According to another aspect, an apparatus that facilitates decoding acommunication signal, comprising a receiver that receives a set ofsymbols containing a plurality of information bits and divides thereceived set of symbols into a plurality of subsets of symbols, adecoder that selects a set of initial a priori values of the inner codedemodulation for each subset of symbols, and an inner code demodulatorthat demodulates each subset of symbols, using the initial a priorivalues of the subset of symbols and an inner code generator matrix, togenerate a plurality of first soft information values. The apparatus mayfurther comprise an interleaver that associates each of the first softinformation values to one of the plurality of information bits using anouter code generator matrix; an outer code demodulator that calculates aplurality of second soft information values, wherein each second softinformation value corresponds to one of the information bits and iscalculated using at least two of the first soft information valuesassociated with the information bit, and a de-interleaver thatdetermines a new set of a priori values of the inner code demodulationfor each subset of symbols, using the second soft information values andthe outer code generator matrix, and replaces the initial a priorivalues with the new a priori values for a next iteration of demodulationof the subsets of symbols.

Another aspect relates to an apparatus that facilitates decoding asignal that enables antenna switching at a wireless terminal, comprisingmeans for receiving a set of symbols containing a plurality ofinformation bits, means for dividing the received set of symbols into aplurality of subsets of symbols, each subset corresponding to the inputof an inner code demodulation, means for selecting a set of initial apriori values of the inner code demodulation for each subset of symbols,and means for demodulating each subset of symbols, using the initial apriori values of the subset of symbols and an inner code generatormatrix, to generate a plurality of first soft information values as theoutput of the inner code demodulation. The apparatus may furthercomprise means for associating each of the first soft information valuesto one of the plurality of information bits using an outer codegenerator matrix, means for calculating a plurality of second softinformation values as the output of the outer code demodulation, whereineach second soft information value corresponds to one of the informationbits and is calculated using at least two of the first soft informationvalues associated with the information bit, means for determining a newset of a priori values of the inner code demodulation for each subset ofsymbols, using the second soft information values and the outer codegenerator matrix, and replacing the initial a priori values with the newa priori values, and means for repeating the demodulating, associating,calculating and determining actions at least once.

Still another aspect relates to a computer-readable medium that storescomputer-executable instructions for receiving a set of symbolscontaining a plurality of information bits, dividing the received set ofsymbols into a plurality of subsets of symbols, selecting a set ofinitial a priori values of the inner code demodulation for each subsetof symbols, and demodulating each subset of symbols, using the initial apriori values of the subset of symbols and an inner code generatormatrix, to generate a plurality of first soft information values. Theinstructions may further comprise associating each of the first softinformation values with one of the plurality of information bits usingan outer code generator matrix, calculating a plurality of second softinformation values, wherein each second soft information valuecorresponds to one of the information bits and is calculated using atleast two of the first soft information values associated with theinformation bit, determining a new set of a priori values of the innercode demodulation for each subset of symbols, using the second softinformation values and the outer code generator matrix, and replacingthe initial a priori values with the new a priori values, and repeatingthe demodulating, associating, calculating and determining actions atleast once.

Yet another aspect relates to a processor that executescomputer-executable instructions for decoding a signal that enablesantenna switching in a wireless terminal, the instructions comprisingreceiving a set of symbols containing a plurality of information bits,dividing the received set of symbols into a plurality of subsets ofsymbols, selecting a set of initial a priori values of the inner codedemodulation for each subset of symbols, and demodulating each subset ofsymbols, using the initial a priori values of the subset of symbols andan inner code generator matrix, to generate a plurality of first softinformation values. The instructions may further comprise associatingeach of the first soft information values with one of the plurality ofinformation bits using an outer code generator matrix, calculating aplurality of second soft information values, wherein each second softinformation value corresponds to one of the information bits and iscalculated using at least two of the first soft information valuesassociated with the information bit, determining a new set of a priorivalues of the inner code demodulation for each subset of symbols, usingthe second soft information values and the outer code generator matrix,and replacing the initial a priori values with the new a priori values,and repeating the demodulating, associating, calculating and determiningactions at least once.

According to other aspects, a method of encoding a strip symbol fortransmission to a wireless terminal in a wireless communicationenvironment may comprise encoding an information bit vector with anouter code to generate a bit matrix using an outer code generator matrixgenerating a codeword for each row in the bit matrix using an inner codegenerator matrix, and concatenating the generated codewords into asingle codeword. The method may further comprise mapping theconcatenated codeword to a number of modulation symbols, and mapping themodulation symbols to a subset of tones in the strip symbol.

According to another aspect, an apparatus that facilitates encoding astrip symbol for transmission to a wireless terminal in a wirelesscommunication environment may comprise an encoder that encodes aninformation bit vector with an outer code to generate a bit matrix usingan outer code generator matrix, generates a codeword for each row in thebit matrix using an inner code generator matrix, concatenates thegenerated codewords into a single codeword. The apparatus may furthercomprise a processor that maps the concatenated codeword to a number ofmodulation symbols and maps the modulation symbols to a subset of tonesin the strip symbol, and a transmitter that transmits the strip symbol.

Yet another aspect relates to an apparatus that facilitates encoding astrip symbol for transmission to a wireless terminal, comprising meansfor encoding an information bit vector with an outer code to generate abit matrix using an outer code generator matrix, means for generating acodeword for each row in the bit matrix using an inner code generatormatrix, as well as means for concatenating the generated codewords intoa single codeword. The apparatus may additionally comprise means formapping the concatenated codeword to a number of modulation symbols, andmeans for mapping the modulation symbols to a subset of tones in thestrip symbol.

A further aspect relates to a computer-readable medium that storescomputer-executable instructions for encoding an information bit vectorwith an outer code to generate a bit matrix using an outer codegenerator matrix, and generating a codeword for each row in the bitmatrix using an inner code generator matrix. The instructions mayfurther comprise concatenating the generated codewords into a singlecodeword, mapping the concatenated codeword to a number of modulationsymbols, and mapping the modulation symbols to a subset of tones in thestrip symbol.

According to still a further aspect, a processor that executescomputer-executable instructions for encoding a strip symbol fortransmission to a wireless device may execute instructions comprisingencoding an information bit vector with an outer code to generate a bitmatrix using an outer code generator matrix, generating a codeword foreach row in the bit matrix using an inner code generator matrix, andconcatenating the generated codewords into a single codeword. Theprocessor may further execute instructions for mapping the concatenatedcodeword to a number of modulation symbols, and mapping the modulationsymbols to a subset of tones in the strip symbol.

According to still other aspects, a method of permitting antennaswitching in a wireless terminal in a wireless communication environmentmay comprise performing a coherent demodulation protocol during a secondtransmission time period of a first superslot and estimating an SNR fora first antenna, switching to at least a second antenna at the end ofthe first superslot, and receiving a bit-interleaved signal havinginformation bits spread across a frequency spectrum for one or morestrip symbols. The method may further comprise estimating an SNR for atleast a second antenna during a first transmission time period of asubsequent super slot, performing a non-coherent detection protocolduring SNR estimation for the at least second antenna, comparing theSNRs for each of the antennas, and selecting an antenna for thesubsequent superslot as a function of the estimated SNRs.

According to another aspect, an apparatus that facilitates antennaswitching in a wireless terminal may comprise a coherent demodulatorthat demodulates a signal received during a second transmission periodof a first superslot, a receiver that receives a bit-interleaved signalhaving information bits spread across a frequency spectrum for one ormore strip symbols, and a processor that estimates an SNR for a firstantenna during the first superslot, switches to at least a secondantenna at the end of the first superslot, and estimates an SNR for atleast the second antenna during a first transmission period of a secondsuperslot. The apparatus may further comprise a non-coherent demodulatorthat demodulates the strip channel during SNR estimation for the atleast second antenna, wherein the processor compares the SNRs for eachof the antennas and selects an antenna for the second superslot as afunction of the estimated SNRs.

Another aspect relates to an apparatus that facilitates antennaswitching in a wireless terminal in a wireless communicationenvironment, comprising means for performing a coherent demodulationprotocol during a second transmission time period of a first superslotand estimating an SNR for a first antenna, means for switching to atleast a second antenna at the end of the first superslot, and means forreceiving a bit-interleaved signal having information bits spread acrossa frequency spectrum for one or more strip symbols. The apparatus mayadditionally comprise means for estimating an SNR for at least a secondantenna during a first transmission time period of a subsequentsuperslot, means for performing a non-coherent detection protocol duringSNR estimation for the at least second antenna, means for comparing theSNRs for each of the antennas, and means for selecting an antenna forthe second superslot as a function of the estimated SNRs.

Yet another aspect relates to a computer-readable medium having storedthereon computer-readable instructions for performing a coherentdemodulation protocol during a first superslot and estimating an SNR fora first antenna, switching to a second antenna at the end of the firstsuperslot, and receiving a bit-interleaved signal having informationbits spread across a frequency spectrum for one or more strip symbols.The instructions may further comprise estimating an SNR for at least asecond antenna during a first transmission time period of a subsequentsuperslot, performing a non-coherent detection protocol during SNRestimation for the at least second antenna, comparing the SNRs for eachof the antennas, and selecting an antenna for a second transmissionperiod of the subsequent superslot as a function of the estimated SNRs.

According to a further aspect, a processor that executes instructionsfor switching between multiple receive antennas in a wireless terminalmay execute instructions comprising performing a coherent demodulationprotocol during a second transmission time period of a first superslotand estimating an SNR for a first antenna, switching to at least asecond antenna at the beginning of a first transmission time period of asubsequent superslot, receiving a bit-interleaved signal havinginformation bits spread across a frequency spectrum for one or morestrip symbols, and estimating an SNR for at least a second antennaduring the first transmission time period of the subsequent superslot.The processor may further execute instructions for performing anon-coherent detection protocol during SNR estimation for the at leastsecond antenna, comparing the SNRs for each of the antennas, andselecting an antenna for a second transmission period of the subsequentsuperslot as a function of the estimated SNRs.

To the accomplishment of the foregoing and related ends, certainillustrative aspects are described herein in connection with thefollowing description and the annexed drawings. These aspects areindicative, however, of but a few of the various ways in which theprinciples of the claimed subject matter may be employed and the claimedsubject matter is intended to include all such aspects and theirequivalents. Other advantages and novel features may become apparentfrom the following detailed description when considered in conjunctionwith the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a transmission channel overview with respect to timethat facilitates to facilitate understanding of strip symbol structureand wireless terminal antenna analysis, in accordance with one or moreaspects described herein.

FIG. 2 illustrates a system comprising components in an exemplarywireless terminal comprising a receiver RF chain, in accordance withvarious aspects presented herein.

FIG. 3 illustrates a system with various components in a wirelessterminal comprising a receiver RF chain, in accordance with variousaspects presented herein.

FIG. 4 is an illustration of a system that facilitates performingmultiple iterations of a soft demodulation and interleaving protocol torefine a received signal and permit antenna switching in a wirelessdevice with multiple antennas and a single receiver chain, in accordancewith one or more aspects.

FIG. 5 is an illustration of a methodology for performing antennaswitching in a wireless device with multiple receive antennas and asingle receiver chain, in accordance with one or more aspects.

FIG. 6 illustrates a methodology for decoding a communication signalusing an iterative SISO non-coherent demodulation protocol to demodulateand interleave concatenated code, in accordance with one or moreaspects.

FIG. 7 is an illustration of a methodology for encoding a communicationsignal comprising a strip symbol for transmission to a wirelessterminal, in accordance with one or more aspects.

FIG. 8 illustrates a system that facilitates antenna switching in awireless terminal with multiple receive antennas per receive chain, in acommunication environment, in accordance with one or more aspectsdescribed herein.

FIG. 9 illustrates a system that facilitates decoding concatenated-codesignals received at a wireless terminal by performing an iterativesoft-demodulation and interleaving algorithm, in accordance with variousaspects.

FIG. 10 is an illustration of a system that facilitates encoding a stripsymbol in a transmission signal for a wireless terminal, in accordancewith various aspects.

FIG. 11 illustrates a network diagram of an exemplary communicationssystem implemented in accordance with the present invention.

FIG. 12 illustrates an exemplary base station implemented in accordancewith the present invention.

FIG. 13 illustrates an exemplary wireless terminal implemented inaccordance with the present invention.

FIG. 14 is an illustration of a wireless communication environment thatcan be employed in conjunction with the various systems and methodsdescribed herein.

DETAILED DESCRIPTION

The claimed subject matter is now described with reference to thedrawings, wherein like reference numerals are used to refer to likeelements throughout. In the following description, for purposes ofexplanation, numerous specific details are set forth in order to providea thorough understanding of the claimed subject matter. It may beevident, however, that such subject matter may be practiced withoutthese specific details. In other instances, well-known structures anddevices are shown in block diagram form in order to facilitatedescribing the claimed subject matter.

Furthermore, various aspects are described herein in connection with auser device. A user device can also be called a system, a subscriberunit, subscriber station, mobile station, mobile device, remote station,remote terminal, access terminal, user terminal, terminal, user agent,or user equipment. A user device can be a cellular telephone, a cordlesstelephone, a Session Initiation Protocol (SIP) phone, a wireless localloop (WLL) station, a PDA, a handheld device having wireless connectioncapability, or other processing device connected to a wireless modem.

Moreover, aspects of the claimed subject matter may be implemented as amethod, apparatus, or article of manufacture using standard programmingand/or engineering techniques to produce software, firmware, hardware,or any combination thereof to control a computer or computing componentsto implement various aspects of the claimed subject matter. The term“article of manufacture” as used herein is intended to encompass acomputer program accessible from any computer-readable device, carrier,or media. For example, computer readable media can include but are notlimited to magnetic storage devices (e.g., hard disk, floppy disk,magnetic strips . . . ), optical disks (e.g., compact disk (CD), digitalversatile disk (DVD) . . . ), smart cards, and flash memory devices(e.g., card, stick, key drive . . . ). Additionally it should beappreciated that a carrier wave can be employed to carrycomputer-readable electronic data such as those used in transmitting andreceiving voice mail or in accessing a network such as a cellularnetwork. Of course, those skilled in the art will recognize manymodifications may be made to this configuration without departing fromthe scope or spirit of what is described herein.

Various aspects described herein relate to coding and modulation toimprove frequency diversity in a wireless communication environment,such as an orthogonal frequency division multiplexing communicationenvironment. For instance, information bits may be spread across abandwidth spectrum through a bit-interleaving protocol, and coding andmodulation may be performed to facilitate performing a non-coherentdemodulation protocol at a receiver, thereby mitigating a need forchannel state information. Soft demodulation techniques may be utilizedin conjunction with concatenated code t permit a wireless terminal toswitch between antennas when a strip channel is received throughmultiple antennas.

FIG. 1 illustrates a transmission channel overview 100 with respect totime that facilitates the understanding of strip symbol structure andwireless terminal antenna analysis, in accordance with one or moreaspects described herein. The transmission channel 100 comprises a stripsymbol 102, which may comprise, for example, 113 tones, 56 of which maybe utilized to transmit data, training information etc., and have anon-zero energy associated with them, while the remaining tones are zeroenergy tones, known as null tones, that do not carry any signaltransmission energy. In some embodiments, the tones may be divided intoa plurality of (e.g., eight) tone subsets, for example tone set 104.Each tone set includes 7 non-zero energy tones and possibly null tones.In each tone subset, the 7 non-zero energy tones may be interspersedwith null tones. As illustrated, strip symbol 102 comprises 113 tones,and a tone subset 104 includes non-zero energy tones, numbered 1-7 andinterspersed with null tones (labeled as “X”). In some embodiments, eachtone subset 104 may comprise a training tone 106 on which a known symbolis transmitted to facilitate channel estimation. Training tone 106 maybe a tone with a different non-zero energy level than the other non-zeroenergy tones in tone subset 104, and may be consistent between tone setsand/or strip symbols (e.g., always tone 3, always to 5, etc.) or mayvary between tone sets and/or strip symbols. According to an example,tone 4 may be a training tone in all tone subsets in all strip channels.According to another example, tone 3 may be a training tone in all tonesets in a first strip symbol, tone 4 may be a training tone in all tonesubsets in a second strip symbol, yet another tone (e.g., any tone 1-7)may be a training tone in a third strip symbol, and so on. According toyet another example, training tones in different subsets may'be randomlyassigned and/or selected. Furthermore, any permutation of trainingtones, tone sets, and strip symbols may be implemented, so long as eachtone set has a training symbol. According to some aspects, the trainingtone 106 is the middle tone among the 7 non-zero energy tones in thetone subset 104. Strip symbol 108 follows strip symbol 102. In someembodiments, the set of non-zero energy tones in strip symbol 102 isdifferent from the set of non-zero energy tones in strip symbol 108.

Strip symbols 102 and 108 may be transmitted at the beginning portion ofa superslot (e.g., approximately 11.4 milliseconds long). Consider awireless terminal equipped with multiple antennas. In FIG. 1, asuperslot includes a first time period in which the strip symbols aresent and a second time period in which the non-strip symbols are sent.For example, the first superslot of FIG. 1 includes strip symbols 102and 108 as the first time period and the non-strip symbols in theremaining time period as the second time period.

Suppose that the second time period of the first superslot is receivedby a wireless terminal over a first channel, H₁, via a first antenna,Antenna 1. In one or more embodiments, a pilot signal is sent in thesecond time period of first superslot. The wireless terminal can thusestimate the channel H1 and use a coherent demodulation protocol,denoted as F₁, to decode the received signal. The wireless terminal mayfurther evaluate the value of SNR for Antenna 1.

Then, in the first time period of the second superslot, the wirelessterminal may switch to use different antennas, e.g., antenna 2 in thefirst strip symbol of the second superslot and antenna 3 in the secondstrip symbol of the second superslot, to receive the signal. As aresult, the channel is changed to H2 and H3 in the first and secondstrip symbols respectively, as shown in FIG. 1. Note that channel H2 orH3 may be different from channel H1 due to the change of the receiveantenna. Therefore, the channel estimation of H1 obtained in the firstsuperslot may not be applicable for channel H2 or H3. Hence, thewireless terminal uses a non-coherent demodulation protocol, F₂, todecode the received signal in the strip symbols. The term “non-coherent”means that the modulation of the signal received in the strip symbolsdoes not depend on the signal received in a preceding time period, e.g.,in the second time period of the first superslot. The wireless terminalmay further evaluate an SNR for one or more other antennas and/orchannels (e.g., H₂, H₃, etc.) received thereby. SNRs may be measured,for instance, during the zero-energy tones (e.g., interference may bequantified) and null tones in each strip symbol. The SNRs for the one ormore other antennas may be compared to the SNR for the first antenna,determined during the previous superslot, and the wireless terminal mayswitch to the antenna (Antenna X shown in FIG. 1) as a function of thecomparison of the measured SNRs. For example, the wireless terminal mayselect the antenna of the highest measured SNR to be used in the secondtime period of the second superslot. The above procedure may repeat inthe subsequent superslots to provide an iterative method by whichantenna reception capability is continuously monitored and evaluated toenable a wireless terminal with multiple antennas to switch between themwhile utilizing a single receiver chain.

In accordance with some aspects, a three-antenna wireless terminal canreceive a signal with two strip symbols 102 and 108 at the beginning ofeach superslot to permit non-coherent demodulation of two unusedantennas at each superslot. According to this example, the wirelessterminal uses one antenna to receive non-strip symbols in a superslot,uses coherent modulation to decode non-strip symbols, and measures theSNR. The wireless terminal may switch to the other two unused antennasduring the strip symbols of the subsequent superslot and perform thenon-coherent demodulation protocol on each strip symbol to decode thesignal. The wireless terminal further determines the SNR for therespective antennas using the strip symbols. The wireless terminal thenselects one antenna to use in the non-strip symbols in the subsequentsuperslot based on the measured SNRs of the three antennas. It will beappreciated that while FIG. 1 and the foregoing example relate to a3-receive-antenna wireless terminal, more or fewer receive antennas maybe utilized and a corresponding number of strip symbols may be encodedand transmitted by a base station and received by the wireless terminalto facilitate antenna switching.

Encoding and/or modulation of the strip symbols may occur in variousmanners in conjunction with one or more aspects. Decoding of the stripsymbols need not rely on the use of preceding symbols. In someembodiments, the strip symbols may be encoded with a vector, low-densityparity check (LDPC) encoding scheme. In particular, the input is anumber of information bits, e.g., 60 bits, and the output is a number ofcoded bits, e.g., 288 bits. The 60-bit vector may be expanded into a64-bit vector by adding four zeros at the end of the information vector,which may be denoted as u=[u₅₉, u₅₈, . . . , u₀], where u₅₉ is the mostsignificant bit (MSB) and u₀ is the least significant bit (LSB). Theexpanded information vector may then be denoted as u=[u₅₉, u₅₈, . . . ,u₀, 0, 0, 0, 0]. A 304-bit codeword vector x=[x₃₀₃, x₃₀₂, . . . , x₀]may be formed from a vector LDPC codes with certain parity check matrix,where x₃₀₃ is the MSB and x₀ is the LSB. A 288-bit output vector may beobtained by shortening the codeword vector x. For instance, the 12 mostsignificant bits in the codeword may be punctured so that the next 288bits in the codeword become the output vector, and the remaining 4 LSBsare similarly punctured. The output vector is given as y=[x₂₉₁, x₂₉₀, .. . , x₄], and may be mapped to 288 modulation symbols using the BPSKmodulation scheme.

The 288 modulation symbols are sent in 6 strip symbols, each for 48modulation symbols. That is, of the 56 available non-zero energytone-symbols in each strip symbol, 8 are training tone symbols (one pertone set), resulting in 48 tone-symbols to which modulation symbols maybe mapped. In the aspect shown in FIG. 1, a strip symbol comprises 56non-zero energy tones, which are divided into 8 tone subsets and eachsubset comprises 7 non-zero energy tones. In the set of 48 modulationsymbols for a given strip symbol, the first 6 modulation symbols aresent in the first tone subset as follows: the first 3 modulation symbolsare sent in the first 3 tones of the tone subset, the other 3 modulationsymbols are sent in the last 3 tones of the tone subset, and a knownmodulation symbol is sent in the middle tone of the tone subset, whichcan be used by the wireless terminal as a training symbol to learn thechannel. The known symbol may be transmitted as the same power as theremaining 6 modulation symbols, or at a higher power. Similarly, thenext 6 modulation symbols are sent in the second tone subset, and so on.

In another aspect, the strip symbols may be encoded with a concatenatedcode. Specifically, one strip symbol is to encode an information bitvector u=[u₀, u₁, u₂, u₃, u₄]. First, an outer code is used to form a21-bit vector. For example, the outer code can be described using a 7×3matrix, such as:

TABLE 1 ${u_{21} = \begin{bmatrix}{u0} & {u2} & {u4} \\{u1} & {u3} & {u4} \\{u0} & {u1} & {u4} \\{u1} & {u2} & {u3} \\{u0} & {u2} & {u3} \\{u1} & {u3} & {u4} \\{u0} & {u2} & {u4}\end{bmatrix}}\quad$Each row comprises 3 bits. For each row in the matrix, an 8-bit codewordmay be generated using an inner code generator matrix, G_(3,8), such as:11110000,11001100,10101010. For instance, the first row of the 7×3matrix is [u₀, u₂, u₄], and, therefore, the 8-bit codeword is equal to[u₀, u₂, u₄] G_(3,8). A total of seven 8-bit codewords may beconcatenated to form a 56-bit codeword, where the 8 MSBs are generatedfrom the first row of the 7×3 matrix, the next 8 MSBs are generated fromthe second row, and so on. The 56-bit concatenated codeword may then bemapped to 56 modulation symbols, e.g., using the BPSK modulation scheme.The 56 modulation symbols are sent in the non-zero energy tones of astrip symbol respectively. Note that in order to achieve frequencydiversity, the outer code ensures that any information bit (u₀, u₁, u₂,u₃, u₄) appears in multiple rows, which will then be encoded by multipleinner codewords. For example, u₀ appears in the first, third, fifth, andseventh rows. Those codewords will be mapped to tones spanning a widefrequency range in the strip symbol.

In another example, an information vector may be denoted as u=[u₀, u₁ .. . , U₁₃]. First, an outer code is used to form a 21-bit vector. Forexample, the outer code can be described using a 7×3 matrix, such as:

TABLE 2 ${u_{42} = \begin{bmatrix}{u5} & {u1} & {u12} \\{u5} & {u2} & {u0} \\{u2} & {u3} & {u1} \\{u3} & {u10} & {u4} \\{u8} & {u5} & {u6} \\{u0} & {u10} & {u7} \\{u3} & {u7} & {u11} \\{u7} & {u4} & {u8} \\{u8} & {u9} & {u2} \\{u9} & {u4} & {u12} \\{u10} & {u11} & {u6} \\{u11} & {u9} & {u13} \\{u12} & {u13} & {u6} \\{u13} & {u0} & {u1}\end{bmatrix}}\quad$Each row comprises 3 bits. For each row in the matrix, an 8-bit codewordmay be generated using an inner code generator matrix, G_(3,8), such as:11110000,11001100,10101010. For instance, the first row of the 14×3matrix is [u₅, u₁, u₁₂], and, therefore, the 8-bit codeword is equal to[u₅, u₁, u₁₂] G_(3,8). A total of fourteen 8-bit codewords may beconcatenated to form a 112-bit codeword, where the 8 MSBs are generatedfrom the first row of the 14×3 matrix, the next 8 MSBs are generatedfrom the second row, and so on. The 112-bit concatenated codeword maythen be mapped to 112 modulation symbols, e.g., using the BPSKmodulation scheme. The 112 modulation symbols are sent in the non-zeroenergy tones of two strip symbols respectively.

FIG. 2 illustrates a system 200 comprising components in an exemplarywireless terminal comprising a receiver RF chain, in accordance withvarious aspects presented herein. System 200 utilizes a switcher 208 toselect one out of the plurality of N antenna elements (202, 204, 206).Received signals are routed through the selected antenna to the RFreceiver chain, while received signals on the other, non-selected,antennas are not forwarded. Switcher 208 is shown coupled to a firstantenna 202. The switcher may be controlled to switch between antennasbased on various information, including time period boundaries. Thisaspect may be viewed from a functional equivalency standpoint in thatthe switcher 208 may comprise a set of controllable gain elements (notshown) in which one value is set equal to one, corresponding to theselected antenna, and the other values are set equal to zero,corresponding to the other antennas.

FIG. 3 illustrates a system 300 with various components in a wirelessterminal comprising a receiver RF chain, in accordance with variousaspects presented herein. According to some aspects, multiple “compound”antenna patterns are possible. For instance, system 300 includes aplurality of antenna elements (302, 304, 306) coupled to a first set ofgain elements (308, 310, 312), with gain values (G1,1, G2,1, GN,1),respectively. The output of the first set of gain elements (308, 310,312) is input to a first combining circuit 314. Antenna elements (302,304, 306) are also coupled to a second set of gain elements (308′, 310′,312′), with gain values (G1,2, G2,2, GN,2), respectively. The output ofthe second set of gain elements (308′, 310′, 312′) is input to a secondcombining circuit 314′. Additional sets of gain elements each with acorresponding combining circuit may be implemented. System 300 alsoincludes a switcher 316 which couples one of the outputs of one of thecombining circuits (314, 314′) to itself and is coupled to thereceiver's RF chain input.

Each antenna pattern is in effect created by the weighted sum of the Nantenna elements. Different antenna patterns differ in their weighingcoefficients, gain values of the a set of gain elements, e.g., (G1,1,G2,1, . . . , GN,1), (GN,1, G1,2, . . . , GN,2). The weightingcoefficients, sometimes referred to a gain values, can be complex orreal values. The gain values may be fixed, predetermined orprogrammable, adjustable, etc.

FIG. 4 is an illustration of a system 400 that facilitates performingmultiple iterations of a soft demodulation and interleaving protocol todecode a received signal in a non-coherent manner, in accordance withone or more aspects. The signal is encoded with a concatenated code asillustrated in the embodiments of Table 1 and Table 2.

For the concatenated code, it is possible to formulate the overallgenerator matrix and to derive the optimal, e.g., maximal likelihood,decoding algorithm. However, the optimal decoding algorithm may becomputationally complex. The iterative decoder 402 takes advantage ofthe concatenated coding structure and can approach the performance ofthe optimal decoder with a few iterations. Advantageously, thecomplexity is significantly reduced.

The decoder 402 may receive a concatenated code input signal, forexample a strip symbol received in a superslot as described with regardto Table 1 or 2 in FIG. 1, and may initiate a soft-input soft-outputdemodulation protocol that utilizes an inner code demodulator 404, aninterleaver 406, an outer code demodulator 408, and a de-interleaver410. For example, a set of symbols containing a plurality of informationbits may be received by inner code demodulator 404, which may thendivide the received symbol set into a plurality of symbol subsets.Decoder 402 may select a plurality of a priori values for inner codedemodulation of the symbol subsets, and inner code demodulator 404 maydemodulate the symbol subsets using the a priori values and an innercode generator matrix to generate a plurality of soft information outputvalues. The soft information output values may be interleaved byinterleaver 406 and associated with one of the plurality of informationbits by outer code modulator 408 (e.g., using an outer code generatormatrix). De-interleaver 410 may calculate a plurality of second softinformation values as an output of the outer code demodulator 408, whereeach second soft information value corresponds to one of the informationbits and is calculated using at least two of the first soft informationvalues associated with the information bit. The second soft informationvalues may then be utilized to determine a new set of a priori valuesfor use in a next iteration of the inner code demodulation of thereceived input symbols, and so on, as indicated by the circular arrow inFIG. 4.

Consider Table 1 as an example. First, the received signal may bedemodulated for the inner code, whose generator matrix may be given asG_(3,8), to generate the soft decoding values of each row in Table 1, inparticular, the soft values X01, X21, X41 of [u₀, u₂, u₄] of the firstrow, the soft values X12, X32, X42 of [u₁, U₃, u₄] of the second row,and so on. Those soft values are called the output soft values of theinner code (e.g., the inner code demodulator 404).

The outer code demodulator 408 provides an additional coding protectionfor any given information bit. For example, note that for bit u₀ thefirst, third, fifth, and seventh rows all provide the soft values.Ideally those soft values are identical. However, because ofinterference and noise in the received signal, they may not be identicalin the first round of iteration. The interleaver 406, outer codedemodulator 408, and de-interleaver 410 take the output soft values ofthe inner code and calculate the output soft values of the outer code.For example, denote the output soft values of the inner code in thefirst, third, fifth, and seventh rows for bit u₀ to be X01, X03, X05 andX07 respectively. Then for bit u₀, the output soft value of the outercode for the first row, denoted as Y01 may be calculated from X01, X03,X05 and X07, e.g., Y01=average (X03, X05, X07). Similarly, for bit u₀,the output soft value of the outer code for the third row, denoted asY03 may be calculated from X01, X03, X05 and X07, e.g., Y03=average(X01, X05, X07). In another example, one can set Y01 and Y03 to be thesame, e.g., equal to average (X01, X03, X05, X07).

The output soft values of the outer code demodulator are thende-interleaved and provided back to the inner code demodulator 404 toimprove the inner code demodulation. In particular, now the inner codedemodulator 404 can take the original received signal and thede-interleaved output soft values of the outer code into account togenerate the improved soft decoding values of each row. For example, inthe first row, the inner code demodulator 404 uses the original receivedsignal and Y01, Y21, Y41, and generates a new set of X01, X21, and X41.Here, Y01, Y21, Y41 are the output soft values of the outer code forbits u₀, u₂, u₄ of the first row respectively, and X01, X21, and X41 arethe output soft values of the inner code for bits u₀, u₂, u₄ of thefirst row respectively. The above procedure repeats for all the otherrows to generate a new set of the output soft values of the inner code.With the new output soft values of the inner code, the interleaver 406,outer code demodulator 408, and de-interleaver 410 can generate a newset of output soft values of the outer code. The above iterativeprocedure repeats until certain termination criterion is met.

Referring to FIGS. 5-7, methodologies relating to performing aniterative SISO non-coherent demodulation protocol upon a receivedconcatenated code signal to facilitate antenna switching in a wirelessterminal are illustrated. While, for purposes of simplicity ofexplanation, the methodologies are shown and described as a series ofacts, it is to be understood and appreciated that the methodologies arenot limited by the order of acts, as some acts may, in accordance withone or more embodiments, occur in different orders and/or concurrentlywith other acts from that shown and described herein. For example, thoseskilled in the art will understand and appreciate that a methodologycould alternatively be represented as a series of interrelated states orevents, such as in a state diagram. Moreover, not all illustrated actsmay be utilized to implement a methodology in accordance with theclaimed subject matter.

FIG. 5 is an illustration of a methodology 500 for performing antennaswitching in a wireless device with multiple receive antennas and asingle receiver chain, in accordance with one or more aspects. Forexample, method 500 may facilitate performing various actions set forthabove with regard to FIG. 1 in order to achieve antenna switching asdescribed therein. At 502, a coherent demodulation protocol may beperformed during a second transmission period of a first superslot andan SNR for a first antenna may be estimated. For instance, a superslotmay include a first time period in which strip symbols are sent and asecond time period in which the non-strip symbols are sent. For example,the first superslot described above with regard to FIG. 1 includes stripsymbols as the first time period and the non-strip symbols in theremaining time period as the second time period. According to an aspect,a pilot signal may be sent in the second time period of first superslot.The wireless terminal may thus estimate the channel H1 corresponding tothe first antenna and use a coherent demodulation protocol, to decodethe received signal. For example, the wireless device may receive a setof pilots and derive channel estimation, which enables the wirelessdevice to perform coherent demodulation for the signal received in thesecond time period of the first superslot.

At 504, a determination whether the first superslot is complete and/orwhether a first transmission time period of the second superslot isimminent, may be made. If the first superslot is complete, a switch fromthe first antenna to a second antenna may be made, at 506, to assess anSNR there for. In the first time period of the second superslot, thewireless terminal may switch to different antennas, e.g., antenna 2 inthe first strip symbol of the second superslot and antenna 3 in thesecond strip symbol of the second superslot, to receive the signal. As aresult, the channel is changed from H1 to H2 and H3 in the first andsecond strip symbols respectively, as shown above in FIG. 1. Note thatchannel H2 or H3 may be different from channel H1 due to the change ofthe receive antenna. Therefore, the channel estimation of H1 obtained inthe first superslot may not be applicable for channel H2 or H3. Hence,the wireless terminal uses a non-coherent demodulation protocol todecode the received signal in the strip symbols. Thus, at 508, a signal,e.g., modulated with a non-coherent modulation scheme and havinginformation bits spread across a frequency spectrum for one or morestrip symbols, may be received. According to one example, the stripsymbol(s) may comprise concatenated code, but is not limited thereto.

At 510, an SNR for at least a second antenna may be estimated during afirst transmission time period of the second superslot. The firsttransmission time period of the second superslot may correspond to, forexample, one or more strip symbol durations, such as the strip symbolsillustrated at the beginning of the second superslot of FIG. 1. Anon-coherent detection protocol may be performed in the firsttransmission time period of the second superslot, at 512. Thenon-coherent detection protocol uses only the signal received in thefirst transmission time period of the second superslot and does not usethe signal received in any preceding time. The SNR is also estimated forthe at least second antenna. The non-coherent detection protocol may bea protocol with interleaved/de-interleaved information bits as describedwith regard to FIG. 4, above. At 514, a comparison may be made betweenthe SNR estimated for the first antenna during the coherent detectiontime period and the SNR(s) detected for the at least second antennaduring the non-coherent SIS detection time period. Finally, at 516, awireless terminal may switch to the antenna having the highest SNR basedon the comparison at 514. In this manner, a wireless terminal may bepermitted to switch between multiple receive antennas as often as everysuperslot (e.g., 11.4 ms).

According to a related aspect, antenna switching may be a function of apredetermined threshold difference between antenna SNRs. For instance,the difference of SNRs at 514 may be required to exceed some predefinedthreshold (e.g., 0.25 dB, 0.5 dB, 1 dB, etc.) in order to justifyswitching between antennas. According to an example, if the predefinedthreshold is 0.5 dB and the first antenna has an SNR of X dB asestimated at 502, then the SNR of a second antenna as estimated at 510would have to meet or exceed X+0.5 dB to warrant switching from thefirst receive antenna to the second receive antenna.

FIG. 6 illustrates a methodology 600 for decoding a communication signalusing an iterative SISO non-coherent demodulation protocol to demodulateand interleave concatenated code, in accordance with one or moreaspects. For example, method 600 can facilitate iterative demodulationand interleaving of a received concatenated signal as described abovewith regard to FIG. 4. According to the method, a set of symbolscontaining a plurality of information bits may be received at 602. Thereceived symbol set may contain a plurality of information bits, and maybe divided into a plurality of symbol subsets, each of which correspondsto an input for an inner code demodulation protocol, at 604. A pluralityof initial a priori values for inner code demodulation of the symbolsubsets may be selected at 606. At 608, the symbol subsets may bedemodulated using the initial a priori values and an inner codegenerator matrix to generate a plurality of first soft informationvalues. Each of the first soft information values may be associated withone of the plurality of information bits by employing an outer codegenerator matrix, at 610. At 612, plurality of second soft informationvalues may be calculated as an output of the outer code demodulation,where each second soft information value corresponds to one of theinformation bits and is calculated using at least two of the first softinformation values associated with the information bit. At 614, thesecond soft information values may then be utilized to determine a newset of a priori values for use in a next iteration of the inner codedemodulation of the received input symbols, where the initial a priorivalues are replaced by the new a priori values for a subsequentiteration of method 600, starting with demodulation at 608. In thismanner, method 600 provides an iterative series of acts that may beperformed on a received strip symbol (or channel) to effectively decodethe strip symbol via a low-complexity and highly efficient non-coherentSISO protocol.

According to related aspects, the wireless terminal may receive a signalthat has been encoded using a Reed-Muller encoding technique, and mayperform method 600 on the received signal. Additionally, theconcatenated code received by the wireless terminal may exhibit certainproperties associated with such encoding techniques. For instance, thereceived signal may be encoded prior to receipt by the wireless terminalusing an outer code in combination with an inner code comprising atleast two subblocks. Thus, it will be appreciated that method 600facilitates performing a decoding algorithm similar to that performed bydecoder 402 of FIG. 4.

According to other aspects, the set of symbols received at 602 may bedivided into at least two subsets at 604. Additionally, the inner codegenerator matrix employed for each subset may be the same or may bedifferent from subset to subset. A second soft information value for agiven information bit may be an average of two or more first softinformation values associated with the bit.

FIG. 7 is an illustration of a methodology 700 for encoding a stripsymbol to enable mobile antenna switching in a wireless communicationenvironment, in accordance with various aspects. At 702, a bitinformation vector may be encoded using an outer code generator matrixto generate a bit matrix, which may comprise at least two rows and anysuitable number of columns. At 704, a codeword may be generated for eachrow in the bit matrix by implementing an inner code generator matrix,which may comprise a Reed-Muller code but is not limited thereto. Theinner code generator matrix may be the same for all rows in the bitmatrix or may be different from row to row. At 706, the codewordsgenerated at 704 may be concatenated into a single codeword. Theconcatenated codeword may be mapped to a number of modulation symbols,at 708. Modulation symbols may be mapped to a subset of tones in thestrip channel at 710. The subset of tones to which modulation symbolsare mapped may be predetermined. Additionally, strip symbol tones towhich modulation symbols are not mapped may be transmitted at azero-energy level when the strip symbol is transmitted. According to anexample, approximately 20% or more of the tones in the strip symbol maybe transmitted at a zero-energy level. In this manner, method 700 may beutilized to facilitate performing various encoding actions, such asthose described above with regard to FIG. 1, and any and all suchactions may be performed in conjunction with method 700.

FIG. 8 illustrates a system 800 that facilitates antenna switching in awireless terminal with multiple receive antennas per receive chain, in acommunication environment, in accordance with one or more aspectsdescribed herein. System 800 is represented as a series of interrelatedfunctional blocks, which can represent functions implemented by aprocessor, software, or combination thereof (e.g., firmware). Forexample, system 800 may provide modules for performing various acts suchas are described above with regard to FIG. 1. System 800 comprises amodule for performing coherent demodulation 802 during first superslotand for estimating SNR for a first antenna. System 800 additionallycomprises a module for determining whether a first superslot is ending804 and a module for switching to a next (e.g. at least a second)antenna 806. System 800 further comprises a module for receivingbit-interleaved, concatenated strip symbol(s) 808, as well as a modulefor estimating SNR 810 for at least a second antenna and a module forperforming non-coherent demodulation 812 for the at least secondantenna. System 800 still further comprises a module for comparing SNRs814 for antennas for which SNRs have been estimated, and a module forselecting an antenna 816 for receiving signal(s) during a subsequentsuperslot as a function of SNR comparison. It is to be understood thatsystem 800 and the various a module comprised thereby may carryout themethods described above and/or may impart any necessary functionality tothe various systems described herein.

FIG. 9 illustrates a system 900 that facilitates decodingconcatenated-code signals received at a wireless terminal by performingan iterative soft-demodulation and interleaving algorithm, in accordancewith various aspects. System 900 is represented as a series ofinterrelated functional blocks, which can represent functionsimplemented by a processor, software, or combination thereof (e.g.,firmware). For example, system 900 may provide modules for performingvarious acts such as are described above with regard to FIG. 4. System900 comprises a module for receiving 902 a set of symbols, which mayhave been encoded using a concatenated code, and a module 904 fordividing 904 the received set of symbols into a plurality of subsets.System 900 further comprises a module for selecting 906 an initial setof a priori values, which may be utilized by a module for demodulating908, in conjunction with an inner code generator matrix, to generate afirst set of soft information values. System 900 further comprises amodule for associating 910 each of the first soft information valueswith one of the plurality of information bits contained in the receivedset of symbols using an outer code generator matrix. A module forcalculating 912 may calculate a second set of soft information valuesfor an information bit using at least two of the first soft informationvalues associated with the bit. A module for determining 914 may thendetermine a new set of a priori values as a function of the second setof soft information values, which may replace the initial set of apriori values for a next iteration of demodulating, associating,calculating, and determining by respective modules 908, 910, 912, and914. It is to be understood that system 900 and the various modulescomprised thereby may carryout the methods described above and/or mayimpart any necessary functionality to the various systems describedherein.

FIG. 10 illustrates a system that facilitates encoding a concatenatedcode strip symbol that enables antenna switching by a wireless terminalin a wireless communication environment, in accordance with one or moreaspects. System 1000 is represented as a series of interrelatedfunctional blocks, which can represent functions implemented by aprocessor, software, or combination thereof (e.g., firmware). Forexample, system 1000 may provide modules for performing various actssuch as are described above with regard to FIG. 7. System 1000 comprisesa module for encoding 1002 an information bit vector with an outer codeto generate a bit matrix. System 1000 further comprises a module forgenerating 1004 a codeword for each row in the bit matrix using an innercode generator matrix. Additionally, system 1000 may comprise a modulefor concatenating 1006 codewords into a single codeword. A concatenatedcodeword may be mapped to a number of modulation symbols by a module formapping a concatenated codeword 1008. Additionally, a module for mappingmodulation symbols 1010 may map the modulation symbols to a subset oftones in the strip symbol. It is to be understood that system 1000 andthe various modules comprised thereby may carryout the methods describedabove and/or may impart any necessary functionality to the varioussystems described herein.

FIG. 11 shows an exemplary communication system 1100 implemented inaccordance with the present invention including multiple cells: cell 11102, cell M 1104. Note that neighboring cells 1102, 1104 overlapslightly, as indicated by cell boundary region 1168, thereby providingthe potential for signal interference between signals being transmittedby base stations in neighboring cells. Each cell 1102, 1104 of exemplarysystem 1100 includes three sectors. Cells which have not be subdividedinto multiple sectors (N=1), cells with two sectors (N=2) and cells withmore than 3 sectors (N>3) are also possible in accordance with theinvention. Cell 1102 includes a first sector, sector 1 1110, a secondsector, sector 2 1112, and a third sector, sector 3 1114. Each sector1110, 1112, 1114 has two sector boundary regions; each boundary regionis shared between two adjacent sectors. Sector boundary regions providethe potential for signal interference between signals being transmittedby base stations in neighboring sectors. Line 1116 represents a sectorboundary region between sector 1 1110 and sector 2 1112; line 1118represents a sector boundary region between sector 2 1112 and sector 31114; line 1120 represents a sector boundary region between sector 31114 and sector 1 1110. Similarly, cell M 1104 includes a first sector,sector 1 1122, a second sector, sector 2 1124, and a third sector,sector 3 1126. Line 1128 represents a sector boundary region betweensector 1 1122 and sector 2 1124; line 1130 represents a sector boundaryregion between sector 2 1124 and sector 3 1126; line 1132 represents aboundary region between sector 3 1126 and sector 1 1122. Cell 1 1102includes a base station (BS), base station 1 1106, and a plurality ofend nodes (ENs) in each sector 1110, 1112, 1114. Sector 1 1110 includesEN(1) 1136 and EN(X) 1138 coupled to BS 1106 via wireless links 1140,1142, respectively; sector 2 1112 includes EN(1′) 1144 and EN(X′) 1146coupled to BS 1106 via wireless links 1148, 1150, respectively; sector 31126 includes EN(1″) 1152 and EN(X″) 1154 coupled to BS 1106 viawireless links 1156, 1158, respectively. Similarly, cell M 1104 includesbase station M 1108, and a plurality of end nodes (ENs) in each sector1122, 1124, 1126. Sector 1 1122 includes EN(1) 1136′ and EN(X) 1138′coupled to BS M 1108 via wireless links 1140′, 1142′, respectively;sector 2 1124 includes EN(1′) 1144′ and EN(X′) 1146′ coupled to BS M1108 via wireless links 1148′, 1150′, respectively; sector 3 1126includes EN(1″) 1152′ and EN(X″) 1154′ coupled to BS 1108 via wirelesslinks 1156′, 1158′, respectively. System 1100 also includes a networknode 1160 which is coupled to BS1 1106 and BS M 1108 via network links1162, 1164, respectively. Network node 1160 is also coupled to othernetwork nodes, e.g., other base stations, AAA server nodes, intermediatenodes, routers, etc. and the Internet via network link 1166. Networklinks 1162, 1164, 1166 may be, e.g., fiber optic cables. Each end node,e.g. EN 1 1136 may be a wireless terminal including a transmitter aswell as a receiver. The wireless terminals, e.g., EN(1) 1136 may movethrough system 1100 and may communicate via wireless links with the basestation in the cell in which the EN is currently located. The wirelessterminals, (WTs), e.g. EN(1) 1136, may communicate with peer nodes,e.g., other WTs in system 1100 or outside system 1100 via a basestation, e.g. BS 1106, and/or network node 1160. WTs, e.g., EN(1) 1136may be mobile communications devices such as cell phones, personal dataassistants with wireless modems, etc. Each base station performs tonesubset allocation using a different method for the strip-symbol periodsin accordance with the invention, from the method employed forallocating tones and determining tone hopping in the rest symbolperiods, e.g., non strip-symbol periods. The wireless terminals use thetone subset allocation method of the present invention along withinformation received from the base station, e.g., base station slope ID,sector ID information, to determine the tones that they can use toreceive data and information at specific strip-symbol periods. The tonesubset allocation sequence is constructed, in accordance with theinvention to spread the inter-sector and inter-cell interference acrosseach of the tones.

FIG. 12 illustrates an exemplary base station 1200 in accordance withthe present invention. Exemplary base station 1200 implements the tonesubset allocation sequences of the present invention, with differenttone subset allocation sequences generated for each different sectortype of the cell. The base station 1200 may be used as any one of thebase stations 1126, 1128 of the system 1120 of FIG. 11. The base station1200 includes a receiver 1202, a transmitter 1204, a processor 1206,e.g., CPU, an input/output interface 1208 and memory 1210 which arecoupled together by a bus 1209 over which the various elements 1202,1204, 1206, 1208, and 1210 may interchange data and information.

Sectorized antenna 1203 coupled to receiver 1202 is used for receivingdata and other signals, e.g., channel reports, from wireless terminalstransmissions from each sector within the base station's cell.Sectorized antenna 1205 coupled to transmitter 1204 is used fortransmitting data and other signals, e.g., control signals, pilotsignal, beacon signals, strip symbols in during a first transmissiontime period of a superslot, etc. to wireless terminals 1300 (see FIG.13) within each sector of the base station's cell. In variousembodiments of the invention, base station 1200 may employ multiplereceivers 1202 and multiple transmitters 1204, e.g., an individualreceivers 1202 for each sector and an individual transmitter 1204 foreach sector. The processor 1206, may be, e.g., a general purpose centralprocessing unit (CPU). Processor 1206 controls operation of the basestation 1200 under direction of one or more routines 1218 stored inmemory 1210 and implements the methods of the present invention. I/Ointerface 1208 provides a connection to other network nodes, couplingthe BS 1200 to other base stations, access routers, AAA server nodes,etc., other networks, and the Internet. Memory 1210 includes routines1218 and data/information 1220.

Data/information 1220 includes data 1236, concatenation encodinginformation 1238 including downlink strip-symbol time information 1240and downlink tone information 1242, and wireless terminal (WT) data/info1244 including a plurality of sets of WT information: WT 1 info 1246 andWT N info 1260. Each set of WT info, e.g., WT 1 info 1246 includes data1248, terminal ID 1250, sector ID 1252, uplink channel information 1254,downlink channel information 1256, and mode information 1258.

Routines 1218 include communications routines 1222 and base stationcontrol routines 1224. Base station control routines 1224 includes astrip channel encoder routine, which may comprise a concatenationencoding routine 1228 that may be implemented by encoder 1214. Theconcatenation encoding routine 1228 may facilitate performing encoderactions similar to those described above with regard to FIG. 1.

Data 1236 includes data to be transmitted that will be sent to encoder1214 of transmitter 1204 for encoding prior to transmission to WTs, andreceived data from WTs that has been processed through decoder 1212 ofreceiver 1202 following reception. Downlink strip-symbol timeinformation 1240 includes the frame synchronization structureinformation, such as the superslot, beaconslot, and ultraslot structureinformation and information specifying whether a given symbol period isa strip-symbol period, and if so, the index of the strip-symbol periodand whether the strip-symbol is a resetting point to truncate the tonesubset allocation sequence used by the base station. Downlink toneinformation 1242 includes information including a carrier frequencyassigned to the base station 1200, the number and frequency of tones,and the set of tone subsets to be allocated to the strip-symbol periods,and other cell and sector specific values such as slope, slope index andsector type.

Data 1248 may include data that WT1 1300 has received from a peer node,data that WT 1 1300 desires to be transmitted to a peer node, anddownlink channel quality report feedback information. Terminal ID 1250is a base station 1200 assigned ID that identifies WT 1 1300. Sector ID1252 includes information identifying the sector in which WT1 1300 isoperating. Sector ID 1252 can be used, for example, to determine thesector type. Uplink channel information 1254 includes informationidentifying channel segments for WT1 1300 to use, e.g., uplink trafficchannel segments for data, dedicated uplink control channels forrequests, power control, timing control, etc. Each uplink channelassigned to WT1 1300 includes one or more logical tones, each logicaltone following an uplink hopping sequence in accordance with the presentinvention. Downlink channel information 1256 includes informationidentifying channel segments to carry data and/or information to WT11300, e.g., downlink traffic channel segments for user data. Eachdownlink channel assigned to WT1 1300 includes one or more logicaltones, each following a downlink hopping sequence. Mode information 1258includes information identifying the state of operation of WT1 1300,e.g. sleep, hold, on. Communications routines 1222 control the basestation 1200 to perform various communications operations and implementvarious communications protocols. Base station control routines 1224 areused to control the base station 1200 to perform basic base stationfunctional tasks, e.g., signal generation and reception, scheduling, andto implement the steps of the method of the present invention includingtransmitting signals to wireless terminals using the tone subsetallocation sequences of the present invention during the strip-symbolperiods.

FIG. 13 illustrates an exemplary wireless terminal (end node) 1300 whichcan be used as any one of the wireless terminals (end nodes), e.g.,EN(1) 1136, of the system 1100 shown in FIG. 11. Wireless terminal 1300implements the tone subset allocation sequences, in accordance with thepresent invention. The wireless terminal 1300 includes a receiver 1302including a decoder 1312 (e.g., which may be similar to the decoder 402of FIG. 4), a transmitter 1304 including an encoder 1314, a processor1306, and memory 1308 which are coupled together by a bus 1310 overwhich the various elements 1302, 1304, 1306, 1308 can interchange dataand information. An antenna 1303 used for receiving signals from a basestation 1200 is coupled to receiver 1302. An antenna 1305 used fortransmitting signals, e.g., to base station 1200 is coupled totransmitter 1304.

The processor 1306, e.g., a CPU controls the operation of the wirelessterminal 1300 and implements methods of the present invention byexecuting routines 1320 and using data/information 1322 in memory 1308.Data/information 1322 includes user data 1334, user information 1336,and demodulation/interleaving information 1350. User data 1334 mayinclude data, intended for a peer node, which will be routed to encoder1314 for encoding prior to transmission by transmitter 1304 to basestation 1200, and data received from the base station 1200 which hasbeen processed by the decoder 1312 in receiver 1302. User information1336 includes uplink channel information 1338, downlink channelinformation 1340, terminal ID information 1342, base station IDinformation 1344, sector ID information 1346, and mode information 1348.Uplink channel information 1338 includes information identifying uplinkchannels segments that have been assigned by base station 1200 forwireless terminal 1300 to use when transmitting to the base station1200. Uplink channels may include uplink traffic channels, dedicateduplink control channels, e.g., request channels, power control channelsand timing control channels. Each uplink channel include one or morelogic tones, each logical tone following an uplink tone hopping sequencein accordance with the present invention. The uplink hopping sequencesare different between each sector type of a cell and between adjacentcells. Downlink channel information 1340 includes informationidentifying downlink channel segments that have been assigned by basestation 1200 to WT 1300 for use when BS 1200 is transmittingdata/information to WT 1300. Downlink channels may include downlinktraffic channels and assignment channels, each downlink channelincluding one or more logical tone, each logical tone following adownlink hopping sequence, which is synchronized between each sector ofthe cell.

User info 1336 also includes terminal ID information 1342, which is abase station 1200 assigned identification, base station ID information1344 which identifies the specific base station 1200 that WT hasestablished communications with, and sector ID info 1346 whichidentifies the specific sector of the cell where WT 1300 is presentlylocated. Base station ID 1344 provides a cell slope value and sector IDinfo 1346 provides a sector index type; the cell slope value and sectorindex type may be used to derive the uplink tone hopping sequences inaccordance with the invention. Mode information 1348 also included inuser info 1336 identifies whether the WT 1300 is in sleep mode, holdmode, or on mode.

Demodulation/interleaving information 1350 includes downlinkstrip-symbol time information 1352 and downlink tone information 1354.Downlink strip-symbol time information 1352 include the framesynchronization structure information, such as the superslot,beaconslot, and ultraslot structure information and informationspecifying whether a given symbol period is a strip-symbol period, andif so, the index of the strip-symbol period and whether the strip-symbolis a resetting point to truncate the tone subset allocation sequenceused by the base station. Downlink tone info 1354 includes informationincluding a carrier frequency assigned to the base station 1000, thenumber and frequency of tones, and the set of tone subsets to beallocated to the strip-symbol periods, and other cell and sectorspecific values such as slope, slope index and sector type.

Routines 1320 include communications routines 1324 and wireless terminalcontrol routines 1326. Communications routines 1324 control the variouscommunications protocols used by WT 1300. Wireless terminal controlroutines 1326 controls basic wireless terminal 1300 functionalityincluding the control of the receiver 1302 and transmitter 1304.Wireless terminal control routines 1326 include an iterative decodingroutine 1328. The iterative decoding routine 1328 includes anon-coherent demodulation routine 1330 for the strip-symbol periods andan interleaving/deinterleaving routine 1332 for that facilitatesdecoding a received strip symbol that has been encoded using aconcatenated encoding technique.

FIG. 14 shows an example wireless communication system 1400. Thewireless communication system 1400 depicts one base station and one userdevice for sake of brevity. However, it is to be appreciated that thesystem can include more than one base station and/or more than one userdevice, wherein additional base stations and/or user devices can besubstantially similar or different from the exemplary base station anduser device described below. In addition, it is to be appreciated thatthe base station and/or the user device can employ the systems and/ormethods described herein.

Referring now to FIG. 14, on a downlink, at access point 1405, atransmit (TX) data processor 1410 receives, formats, codes, interleaves,and modulates (or symbol maps) traffic data and provides modulationsymbols (“data symbols”). A symbol modulator 1415 receives and processesthe data symbols and pilot symbols and provides a stream of symbols.Symbol modulator 1415 multiplexes data and pilot symbols and providesthem to a transmitter unit (TMTR) 1420. Each transmit symbol may be adata symbol, a pilot symbol, or a signal value of zero. The pilotsymbols may be sent continuously in each symbol period. The pilotsymbols can be frequency division multiplexed (FDM), orthogonalfrequency division multiplexed (OFDM), time division multiplexed (TDM),frequency division multiplexed (FDM), or code division multiplexed(CDM).

TMTR 1420 receives and converts the stream of symbols into one or moreanalog signals and further conditions (e.g., amplifies, filters, andfrequency upconverts) the analog signals to generate a downlink signalsuitable for transmission over the wireless channel. The downlink signalis then transmitted through an antenna 1425 to the user devices. At userdevice 1430, an antenna 1435 receives the downlink signal and provides areceived signal to a receiver unit (RCVR) 1440. Receiver unit 1440conditions (e.g., filters, amplifies, and frequency downconverts) thereceived signal and digitizes the conditioned signal to obtain samples.A symbol demodulator 1445 demodulates and provides received pilotsymbols to a processor 1450 for channel estimation. Symbol demodulator1445 further receives a frequency response estimate for the downlinkfrom processor 1450, performs data demodulation on the received datasymbols to obtain data symbol estimates (which are estimates of thetransmitted data symbols), and provides the data symbol estimates to anRX data processor 1455, which demodulates (e.g., symbol demaps),deinterleaves, and decodes the data symbol estimates to recover thetransmitted traffic data. The processing by symbol demodulator 1445 andRX data processor 1455 is complementary to the processing by symbolmodulator 1415 and TX data processor 1410, respectively, at access point1405.

On the uplink, a TX data processor 1460 processes traffic data andprovides data symbols. A symbol modulator 1465 receives and multiplexesthe data symbols with pilot symbols, performs modulation, and provides astream of symbols. A transmitter unit 1470 then receives and processesthe stream of symbols to generate an uplink signal, which is transmittedby the antenna 1435 to the access point 1405.

At access point 1405, the uplink signal from user device 1430 isreceived by the antenna 1425 and processed by a receiver unit 1475 toobtain samples. A symbol demodulator 1480 then processes the samples andprovides received pilot symbols and data symbol estimates for theuplink. An RX data processor 1485 processes the data symbol estimates torecover the traffic data transmitted by user device 1430. A processor1490 performs channel estimation for each active user devicetransmitting on the uplink. Multiple user devices may transmit pilotconcurrently on the uplink on their respective assigned sets of pilotsubcarriers, where the pilot subcarrier sets may be interlaced.

Processors 1490 and 1450 direct (e.g., control, coordinate, manage,etc.) operation at access point 1405 and user device 1430, respectively.Respective processors 1490 and 1450 can be associated with memory units(not shown) that store program codes and data. Processors 1490 and 1450can utilize any of the methodologies described herein. RespectiveProcessors 1490 and 1450 can also perform computations to derivefrequency and impulse response estimates for the uplink and downlink,respectively.

For a software implementation, the techniques described herein may beimplemented with modules (e.g., procedures, functions, and so on) thatperform the functions described herein. The software codes may be storedin memory units and executed by processors. The memory unit may beimplemented within the processor or external to the processor, in whichcase it can be communicatively coupled to the processor via variousmeans as is known in the art.

What has been described above includes examples of one or moreembodiments. It is, of course, not possible to describe everyconceivable combination of components or methodologies for purposes ofdescribing the aforementioned embodiments, but one of ordinary skill inthe art may recognize that many further combinations and permutations ofvarious embodiments are possible. Accordingly, the described embodimentsare intended to embrace all such alterations, modifications andvariations that fall within the spirit and scope of the appended claims.Furthermore, to the extent that the term “includes” is used in eitherthe detailed description or the claims, such term is intended to beinclusive in a manner similar to the term “comprising” as “comprising”is interpreted when employed as a transitional word in a claim.

1. A method of permitting antenna switching in a wireless terminal in awireless communication environment, comprising: performing a coherentdemodulation protocol during a second transmission time period of afirst superslot and estimating an SNR for a first antenna; switching toat least a second antenna at the end of the first superslot; receiving abit-interleaved signal having information bits spread across a frequencyspectrum for one or more strip symbols; estimating an SNR for at least asecond antenna during a first transmission time period of a subsequentsuper slot; performing a non-coherent detection protocol during SNRestimation for the at least second antenna; comparing the SNRs for eachof the antennas; and selecting an antenna for the subsequent superslotas a function of the estimated SNRs.
 2. The method of claim 1, furthercomprising pre-defining a threshold value below which the wirelessterminal does not switch antennas.
 3. The method of claim 2, furthercomprising comparing the threshold value to a difference between the SNRestimated for the first antenna and the SNR estimated for the at leastsecond antenna.
 4. The method of claim 3, further comprising switchingto the at least second antenna if the at least second antenna has an SNRthat is higher than the SNR for the first antenna by an amount equal toor greater than the threshold value.
 5. The method of claim 1, whereinthe received signal has been coded using a concatenated code protocol.6. An apparatus that facilitates antenna switching in a wirelessterminal, comprising: a coherent demodulator that demodulates a signalreceived during a second transmission period of a first superslot; areceiver that receives a bit-interleaved signal having information bitsspread across a frequency spectrum for one or more strip symbols; aprocessor that estimates an SNR for a first antenna during the firstsuperslot, switches to at least a second antenna at the end of the firstsuperslot, and estimates an SNR for at least the second antenna during afirst transmission period of a second superslot; and a non-coherentdemodulator that demodulates the strip channel during SNR estimation forthe at least second antenna; wherein the processor compares the SNRs foreach of the antennas and selects an antenna for the second superslot asa function of the estimated SNRs.
 7. The apparatus of claim 6, whereinthe processor compares a threshold value to a difference between the SNRestimated for the first antenna and the SNR estimated for the at leastsecond antenna.
 8. The apparatus of claim 7, further comprisingswitching to the at least second antenna if the at least second antennahas an SNR that is higher than the SNR for the first antenna by anamount equal to or greater than the threshold value.
 9. The apparatus ofclaim 6, wherein the processor estimates an SNR for the at least secondantenna during zero-energy tones in the strip symbol.
 10. The apparatusof claim 6, wherein the received signal has been coded using aconcatenated code protocol.
 11. An apparatus that facilitates antennaswitching in a wireless terminal in a wireless communicationenvironment, comprising: means for performing a coherent demodulationprotocol during a second transmission time period of a first superslotand estimating an SNR for a first antenna; means for switching to atleast a second antenna at the end of the first superslot; means forreceiving a bit-interleaved signal having information bits spread acrossa frequency spectrum for one or more strip symbols; means for estimatingan SNR for at least a second antenna during a first transmission timeperiod of a subsequent superslot; means for performing a non-coherentdetection protocol during SNR estimation for the at least secondantenna; means for comparing the SNRs for each of the antennas; andmeans for selecting an antenna for the second superslot as a function ofthe estimated SNRs.
 12. The apparatus of claim 11, further comprisingmeans for pre-defining a threshold value below which the wirelessterminal does not switch antennas.
 13. The apparatus of claim 12,further comprising means for comparing the threshold value to adifference between the SNR estimated for the first antenna and the SNRestimated for the at least second antenna and switching to the at leastsecond antenna if the at least second antenna has an SNR that is higherthan the SNR for the first antenna by an amount equal to or greater thanthe threshold value.
 14. The apparatus of claim 11, wherein the receivedsignal has been coded using a concatenated code protocol.
 15. Acomputer-readable medium having stored thereon computer-readableinstructions, the instructions comprising: performing a coherentdemodulation protocol during a first superslot and estimating an SNR fora first antenna; switching to a second antenna at the end of the firstsuperslot; receiving a bit-interleaved signal having information bitsspread across a frequency spectrum for one or more strip symbols;estimating an SNR for at least a second antenna during a firsttransmission time period of a subsequent superslot; performing anon-coherent detection protocol during SNR estimation for the at leastsecond antenna; comparing the SNRs for each of the antennas; andselecting an antenna for a second transmission period of the subsequentsuperslot as a function of the estimated SNRs.
 16. The computer-readablemedium of claim 15, further comprising instructions for pre-defining athreshold value below which the wireless terminal does not switchantennas.
 17. The computer-readable medium of claim 15, wherein thereceived signal has been coded using a concatenated code protocol.
 18. Aprocessor that executes instructions for switching between multiplereceive antennas in a wireless terminal, the instructions comprising:performing a coherent demodulation protocol during a second transmissiontime period of a first superslot and estimating an SNR for a firstantenna; switching to at least a second antenna at the beginning of afirst transmission time period of a subsequent superslot; receiving abit-interleaved signal having information bits spread across a frequencyspectrum for one or more strip symbols; estimating an SNR for at least asecond antenna during the first transmission time period of thesubsequent superslot; performing a non-coherent detection protocolduring SNR estimation for the at least second antenna; comparing theSNRs for each of the antennas; and selecting an antenna for a secondtransmission period of the subsequent superslot as a function of theestimated SNRs.
 19. The processor of claim 18, wherein the receivedsignal has been coded using a concatenated code protocol.